Conversion of lignocellulosic biomass into biogas

ABSTRACT

An anaerobic digestion system for producing biogas from biomass, particularly biomass that is lignocellulosic, and includes two separate and interacting anaerobic reactor environments to solubilize lignocellulosic materials and make them available for conversion to biogas.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 16/194,271, filed Nov. 16, 2018, which claims priority fromU.S. Provisional Application 62/750,221 filed Oct. 24, 2018 and U.S.Provisional Application 62/587,417 filed Nov. 16, 2017, all of which arehereby incorporated by reference. This application also claims priorityto PCT/US18/61695 which claims priority from U.S. ProvisionalApplication 62/750,221 filed Oct. 24, 2018 and U.S. ProvisionalApplication 62/587,417 filed Nov. 16, 2017, all of which are herebyincorporated by reference.

BACKGROUND

Anaerobic digestion is used to convert soluble products into biogaswhich can be used to generate fuels, chemicals, fibers, and energy. Tobe economically viable, and reduce the amount of unconverted biomasswaste, an adequate conversion percentage is desirable. A major problemarises in the digestion of lignocellulosic waste. Lignin is generallyconsidered not available to anaerobic digestion and is largely notconverted. The use of multiple anaerobic digesters to convert biomassinto biogas has been suggested but none of these digestion systems aredesigned specifically to digest lignin, and with these systems mostlignocellulose remains undigestible.

Lignocellulosic biomass is a relatively inexpensive, renewable, andabundant material. However, without some kind of chemical or mechanicalprocessing of lignocellulosic biomass, anaerobic digestion typicallyconverts only one-third of the carbon in the lignocellulosic biomassinto biogas. In addition, the biogas is typically only 60% methane.Anaerobic digestion by microorganisms is effective on hemicellulose-sidechains, but in lignocellulosic biomass that contains cellulose, longglucose chains, these chains are only slowly digested. Further, lignin,a complex polyphenol that can be abundant in plant biomass, is resistantor toxic to many microorganisms.

BRIEF DESCRIPTION OF DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawings(s) will be provided by the Office upon request andpayment of the necessary fee.

FIG. 1 illustrates a diagram of an example reactor according toprinciples described herein.

FIG. 2 illustrates a diagram of an example reactor according toprinciples described herein.

FIG. 3 illustrates a diagram of an example reactor according toprinciples described herein.

FIG. 4 illustrates a diagram of an example reactor according toprinciples described herein.

FIG. 5 illustrates a diagram of an example reactor according toprinciples described herein.

FIG. 6 illustrates a diagram of an example reactor according toprinciples described herein.

FIG. 7 illustrates a diagram of an example reactor according toprinciples described herein.

FIG. 8 illustrates a diagram of an example reactor according toprinciples described herein.

FIG. 9 illustrates a diagram of an example reactor according toprinciples described herein.

FIG. 10 illustrates a diagram of an example reactor according toprinciples described herein.

FIG. 11 illustrates a diagram of an example reactor according toprinciples described herein.

FIG. 12 illustrates a diagram of an example reactor according toprinciples described herein.

FIG. 13 illustrates a diagram of an example reactor according toprinciples described herein.

FIG. 14 illustrates a diagram of an example reactor according toprinciples described herein.

FIGS. 15A and 15B illustrate graphs showing exemplary biogas volume andbiogas rate of production v. time.

FIGS. 16A and 16B illustrate graphs showing exemplary biogas volume andbiogas rate of production v. time.

FIG. 17 illustrates the methane content of the biogas produced bydiffering mixtures of acetate, lactate and glucose.

FIG. 18 illustrates a graph that shows alkalinity within the ASB tankachieved by recycling bicarbonate from the AD tank.

DETAILED DESCRIPTION

The following describes two successive anaerobic digestion environmentsthat are used to treat lignocellulosic biomass;

(1) a high-temperature biological anaerobic digestion environment bythermophilic anaerobic microorganisms and pasteurization ofnon-thermophilic anaerobes or mesophilic anaerobes. This digestion isdescribed here as an anaerobic secretome bioreaction (ASB) environment.

(2) an anaerobic digestion (AD) environment with non-thermophilic ormesophilic anaerobes. An example anaerobic digestion system according toprinciples discussed herein includes an ASB environment and an ADenvironment. The system treats biomass for the production of biogas andincludes structure adapted to receive a feed containing biomass. The ASBenvironment contains thermophilic anaerobic microorganisms that can onlyexist at thermophilic ASB temperature conditions, but thrive and digestlignocellulose. The thermophilic anaerobic microbes metabolize andsolubilize the biomass through hydrolysis, acidogenesis, andacetogenesis to produce products accessible for digestion. Theseproducts include several products, but typically comprise one or more ofacetic acid and lactic acid. As more fully described below, the ASBenvironment can be adjusted to favor acetic acid production over lacticacid production, or vice versa. This in turn determines the amount ofCO₂ in the biogas product. Accordingly, an essentially CO₂ free biogas,or a biogas with a predetermined CO₂ content can be produced.

The ASB environment is of a thermophilic temperature to support growthof the thermophilic anaerobic organisms. The thermophilic anaerobicmicroorganisms thrive at temperatures sufficiently high to damage orkill non-thermophilic or mesophilic microorganisms. The ASB temperaturesaccordingly pasteurize the biomass of non-thermophilic microbes.

A benefit of the ASB temperature, in addition to providing optimizationfor thermophiles and the advantage of pasteurization, is that the growthand pasteurization occurs at a faster rate than would be achieved at anon-thermophilic temperature.

Because of the pasteurization, the ASB environment is essentially freeof non-thermophilic or mesophilic (NT) microbes. NT microbes includethose commonly used in conventional or prior-art treatments and mayoccur naturally in biomass materials. NT microbes may also includecommon pathogens in lignocellulosic waste streams, such as manure. NTmicrobes do not thrive, or usually even survive, thermophilictemperatures. Specific examples of NT microbes include E. coli,Salmonella typhimurium, Salmonella dublin, campylobacter spp., Listeriamonocytogenes, Yersinia enterocolitica, Cryptosporidium parvum, Giardialamblia, enterococcus, Fecal coliform, and enterobacteria. Otherexamples are anticipated.

Many prior-art processes produce waste streams that are contaminatedwith pathogens that were present in the original biomass feed prior totreatment. This creates a disposal problem, as the waste stream may be apathogenic biohazard that cannot be used for other purposes, such assoil remediation for food-crops. The pasteurization temperatures of theASB eliminate this problem

Structure is provided to remove from the ASB environment, ASB treatedbiomass comprising solubilized biomass, liquid effluent, and solideffluent from the ASB environment, and introduce it to the anaerobicdigestion (AD) environment. This structure may also include structure,such as coolers or heat exchangers, to cool the ASB effluent to atemperature suitable for the AD environment. The heat removed from theASB effluent may be recycled, as described below, for example to heatfuture biomass feed for the ASB.

The AD environment is of a temperature to sustain and support growth ofNT anaerobic microbes. After the NT anaerobic microbes are pasteurizedin the ASB environment and thus become inactive in the AD feed,additional anaerobic microbes must be initially introduced or inoculatedinto the AD environment for the AD treatment. This may be accomplishedby any suitable means, such as a direct, inoculation, or through asatellite reservoir described below. The AD environment is notthermophilic and does not sustain or support growth of thermophilic ASBmicroorganisms. The NT anaerobic microbes introduced to the ADenvironment digest the ASB treated biomass through methanogenesis toproduce methane. Unlike prior-art anaerobic digestion processes,difficult or impossible to digest lignocellulosic materials in thebiomass have been converted in the ASB to readily anaerobic digestiblematerials for the AD feed. In addition to methanogenesis in the AD,hydrolysis, acidogenesis, acetogenesis, and other processes may alsooccur.

Moreover, various contents may be introduced or recycled to the ASBenvironment by the AD environment. Furthermore, at least one satellitereservoir may supply contents to at least one of the ASB and ADenvironments according to principles described herein.

A heat recovery system may be used to recover and recycle heat from atleast one environment. For example, at least one heat exchanger may beused to direct heat from at least one environment to at least one otherenvironment. Purification treatments may also be used on contentsproduced by at least one environment. Also, contents may be recycledfrom at least one environment to at least one other environment.

The treatment processes according to principles described hereinadvantageously have lower energy costs compared to current treatmentprocesses, render biomass significantly more available to anaerobictreatment, and introduce no chemical agents that are poisonous orinhibitory to anaerobic microorganisms. The two-part anaerobic digestionenvironments described herein are to treat biomass more completely andquickly without the use of mechanical and chemical pretreatment. It isacknowledged that processes are available that use anaerobic digestionby anaerobic microbes to solubilize biomass into materials that can beconverted into biogas. The microbes may be readily available and oftenoccur naturally with the biomass. A problem with these processes is thatbiomass materials often contain significant amounts of lignocellulosicmaterials that are essentially insoluble under anaerobic digestion.

An example of such a process is disclosed in U.S. Pat. No. 6,342,378 toZhang, wherein digestion is modified to control volatile fatty acidswhich can inhibit the conversion to biogas. However, even with thisimproved digestion system, problems with materials that are unable to besolubilized or digested are significant, as noted in column 8, line 67through column 9, line 13. Materials like rice straw are difficult tobiodegrade. This is due, at least in part, to the plant fibers havinglignin, cellulose, and hemi-cellulose, all of which are water-insoluble.Breakdown of these insoluble materials can be achieved to some degree bychemical hydrolysis or biodegradation. However, the breakdown isseverely inhibited by lignin, cellulose, and hemi-cellulose which formbarriers or seals around materials and which are considerednon-biodegradable by conventional digestion.

Efforts have been made to improve anaerobic digestion of biomass bytreating biomass with chemical or mechanical means beforehand, however,there are several drawbacks. Mechanical treatment systems, such asgrinding and cutting, are generally energy intensive, uneconomical, andonly modestly effective in improving conversion. Chemical treatmentintroduces components, such as acids or bases, to chemically react withbiomass and make it more available to anaerobic digestion. Thesecomponents, however, are often poisonous to anaerobic bacteria and arealso only modestly effective. Strong acids or alkalies used to breakdownor damage lignin actually poison the anaerobic digestion. Any advantagesfrom breaking down the biomass components by the chemicals arecompromised by causing a less than optimal anaerobic environment in thesubsequent anaerobic digestion tank. Chemical means can further createan expensive disposal problem for toxic wastes that result.

There are known microbes that in nature digest lignin, but none havebeen used in a biomass to biogas system, particularly a system that canbe operated on an industrial scale. Because of the ASB treatment priorto the AD treatment, the AD treatment functions in a more efficient andcontrolled manner that is not achievable in conventional anaerobictreatments. In addition, the ASB treated biomass to the AD ispasteurized, free from problems associated with conventional anaerobicdigesters where the composition of the methanogenic consortium cannot becontrolled from contamination from unpasteurized feedstock. The ASBtreatment thus allows customization and optimization of the AD anaerobicmicroorganisms, depending on, for example, the nature of the biomass,process conditions, and other variables.

In contrast to conventional anaerobic digestion, any of certain suitablethermophilic microorganisms that digest lignocellulosic materials can beused in the ASB to biologically treat biomass fed to the AD to make itsignificantly more available to anaerobic digestion. The ASB may occurin a suitable reactor or tank, or any other environment that produces aneffluent comprising at least one of a solubilized biomass, liquideffluent, and solid effluent.

The ASB environment provides an environment where microbes can thrivewithout compromising the environment for subsequent treatment in the ADenvironment by anaerobic methanogenetic microbes. Example microorganismssuitable for the ASB include bacteria or organisms capable of breakingdown lignocellulose (e.g., cellulose, hemicellulose, lignin, etc.).Examples include thermophilic extremophiles found naturally in somehydrothermal pools. A study indicated that the bacteria anaerobicthermophile Caldicellulosiruptor bescii (“C. bescii”) solubilizes 85% oflignocellulose and cellular material. (See “Carbohydrate and lignin aresimultaneously solubilized from untreated switchgrass by microbialaction at high temperature,” Energy and Environmental Science, Issue 7,2013.)

The principles described herein may be applied to carry out the reactionon an industrial scale, providing universal industrial conversion ofbiomass by extremely thermophilic microbes in a treatment that requireslimited or no chemical additions. The ASB/AD digestion is suitable forany biomass containing lignocellulosic materials. Other hard to digestmaterials, such as bacterial cell material and algae may also beadvantageously digested by the ASB/AD system. In an example, the ASB/ADdigestion is applied to giant king grass, mixed green waste, paper,sewage, manure and/or several other feedstocks on a pilot plant scale.In another example, the ASB/AD digestion is scaled to commercialanaerobic digestion systems, such as electrical generation on a megawattscale.

The environment suitable for organisms, such as C. bescii, to thrive andproduce sufficiently large amounts of secretome, is thermophillic. Forexample, in a lab experiment, C. bescii solubilized up to 90% oflignocellulose and cellular material in an ASB environment to make thecarbon accessible for anaerobic digestion. Accordingly, the biomass isheated, either in a previous tank, or in the ASB tank, to a hightemperature that is suitable for the growth and flourishing of ASBorganisms. The ASB environment is unsuitable for growth of anaerobicorganisms usually found in conventional anaerobic digestion.Accordingly, the biomass is effectively pasteurized, with the exceptionof the ASB organisms.

The AD is operated in a similar manner as a conventional anaerobicdigestion system. But, there are significant differences that derivefrom its use together with the ASB. Among others, the AD receives anon-conventional lignocellosic-depleted and optimized predigested feedthat can there be more fully digested and converted to biogas.

Anaerobic digestion involves at least four processes—hydrolysis,acidogenesis, acetogenesis, and methanogenesis (biogas generation). Asingle anaerobic digestion cannot be optimized for all such processes.By separating digestion into two environments, processes such ashydrolysis, acidogenesis, acetogenesis in the ASB can be more quicklyand more completely carried out, thus creating an ideal and readilyavailable biomass for methanogenetic biogas generation in the AD.

The combined ASB and AD is an improved digestion reactor system whichcan achieve a much higher biogas conversion than a conventionalanaerobic system. By digesting the biogas in two radically differentanaerobic environments, rather than one, a more complete digestion ofthe biomass is achieved.

Summary of ASB/AD Digestion System and Method

The ASB/AD digestion systems and methods have several advantages anddifferences over known anaerobic digestion systems, which will bedescribed below and which include, but are not limited to:

-   -   Separation into two anaerobic digestion environments, a hot        thermophilic ASB and a cooler AD,    -   Modification of AD feed by ASB converting lignocellulosic        materials to digestible materials,    -   Material increase of the portion of biomass converted to biogas,        and the rate of conversion. (see Examples below “TESTS OF        DIGESTION SYSTEM”)    -   Control in ASB environment of anaerobic microbes by        pasteurization of all but thermophilic anaerobes and elimination        of pathogenic organisms.    -   The ability to approach or achieve a closed system with a        minimum number of added reagents by, for example, recycling of        carbonate, low energy consumption by heating from biogas        combustion, etc. Several other material and energy recycle        options are available.    -   The ability to select between CO₂ free biogas and CO₂ containing        biogas production.

Definitions

The term “thermophilic” with respect to the ASB environment describes anenvironment where thermophiles or thermophilic microbes thrive, and NTmicrobes are killed or damaged. This can be a temperature above about 45to 65° C., and includes temperatures at which extreme thermophilesthrive, such as 70° C.-75° C. and above. NT microbes, which includemesophilic microbes generally used in prior art biomass digestionprocesses at temperatures between 20 to 45° C. are killed or damaged ina thermophilic environment. Moreover, the thermophilic temperature isfatal to any microbes that are not adapted to high temperatures commonlyfound in natural thermal springs or pools which can have temperaturesof, for example 70° C., 70-75° C., or 75° C. and greater.

The term “tank” refers to an actual tank or other reaction containment,space or environment in which suitable conditions are met. The termfurther includes a suitable continuous or semi-continuous flow reactor,plug-flow reactor, reaction tank, etc.

The term “reactor” refers to at least one tank or set of tanks used inrelation to the treatment of lignocellulosic biomass.

The term “satellite reservoir” refers to a separate, independentreservoir that is configured to maintain and provide at least onemicrobe, nutrient solution, pH adjusting chemical, or other content toanother environment.

The term “environment” is broadly used to include environments thatinclude not only tanks and reservoirs, but other environments forapplying principles discussed herein. Note that “tank”, “reactor”,“environment,” and “satellite reservoir” may be used interchangeablyaccording to principles discussed herein. Each may further perform atleast one of mixing and heating according to principles describedherein.

The term “biogas” refers to gas which may be combusted to generateelectricity and heat, or further processed into renewable natural gasand transportation fuels. Biogas as described herein may include atleast one of methane, pure methane, carbon dioxide, compressed naturalgas (CNG), and other contents known or as described herein.

EXAMPLES

Tests of ASB/AD Digestion System

Example—Dairy Manure Testing Results

A 6% solids solution of dairy manure was ASB treated in the ASB tank for48 hours. After ASB treatment, the material was anaerobically digestedand the rate of biogas production and composition was measured. Acontrol experiment was conducted by heating a 6% solids solution ofdairy manure to 75° C. for 48 hours. Afterward, the solution wasanaerobically digested and the rate of biogas production and compositionwas measured. FIG. 15A shows that ASB treated manure (solid black line)produced 2.5× more biogas than the control (dashed black line). FIG. 15Bshows the rate of biogas production. The maximum rate of biogasproduction from ASB treated manure (filled black circles) was 2.7×larger than the maximum rate of biogas production from the control(filled black triangles). The methane content in ASB treated,anaerobically digested manure was 74% compared to 72% for the control.

Example—Waste Activated Sludge (WAS) Testing Results

A 5% solids solution of WAS was ASB treated in the ASB for 48 hours.After ASB treatment, the material was anaerobically digested and therate of biogas production and composition was measured. A controlexperiment was conducted by heating a 6% solids solution of WAS to 75°C. for 48 hours. Afterward, the solution was anaerobically digested andthe rate of biogas production and composition was measured. FIG. 16Ashows ASB treated WAS (solid black line) produced 2.4× more biogas thanthe control (dashed black line). FIG. 16B shows the rate of biogasproduction. The maximum rate of biogas production from ASB treated WAS(filled black circles) was 2.6× larger than the maximum rate of biogasproduction from the control (filled black triangles). The methanecontent in ASB treated, anaerobically digested WAS was 76% compared to62% for the control. Clearly, it can be appreciated that the treatedbiomass increases biogas production.

ASB/AD Bioreactor System

ASB Tank

In an example, an ASB tank receives biomass to carry out digestion.Turning to FIG. 1, an example reactor is shown in which biomass 258 isfirst supplied to a mixing tank 202. The biomass 258 within the mixingtank 202 is mixed with a mixer as represented by paddles 244 and poweredby a mixing motor 226. The biomass effluent 209 produced by the mixingtank 202 is supplied to the ASB tank 208 as indicated by a black arrow.Note that at least one of water, heat, and mixing may be applied to thebiomass 258 prior to entering the mixing tank 202. In another example,the biomass 258 is fed directly to the ASB tank 208 without the mixingtank 202.

The contents within the example ASB tank 208 are digested and mayfurther be mixed with a mixer as represented by paddles 246 and poweredby a mixing motor 232. Heat may also be applied in the ASB tank 208. ASBtreated biomass 210 that is produced by the ASB tank 208 is supplied tothe AD tank 212 for anaerobic digestion as indicated by a black arrow.The ASB tank 208 may further receive a supply of contents from the ASBsatellite reservoir 236 that is functionally connected to the ASB tank208 and powered by an ASB satellite motor 234. Satellite paddles 248 asshown may be used to stir its contents, such as at least one or more ofbacteria, nutrients, and other matter described herein to facilitate theASB treatment process within the ASB tank 208. Heat may also be appliedto the ASB satellite reservoir 236.

In an example, contents such as CO₂ and bicarbonate 211 that areproduced in the AD tank 212 as powered by motor 238 are recycled back tothe ASB tank 208 as indicated by a black arrow. Mixing may also occur inthe AD tank 212, as provided by paddles 246. The AD treated biomass 240is supplied to a biogas processor 254 which produces biogas 242.

The biomass effluent 209 provided to the ASB tank 208 may contain or beat levels approximating, for example, 10% of the influent solidscontent. Digestion within the ASB tank 208 is accomplished by asecretome of a class of high-temperature thermophilic microorganismsthat cannot be present in sufficient numbers in conventional anaerobicdigestion. A secretome is the set of proteins expressed by an organismand secreted into the extracellular space or onto the surface of theorganism. Any secretome and digestion proteins produced by anaerobicmicroorganisms used in conventional anaerobic digestion only modestlyreact and break down biomass, thus achieving only the modest result thathas been seen with current anaerobic digestion processes.

Within the ASB tank 208, the biomass effluent 209 receives exposure toat least one material comprising a thermophilic anaerobic microbe thatdigests and “solubilizes” at least a portion of the biomass effluent209, including lignocellulose materials, essentially breaking down plantcell structure/walls within the material and making contents of theplant cells available for subsequent anaerobic digestion.

“Lignocellulose” or “lignocellulosic” is meant to describe materialsthat contain lignin, hemi-cellulose, and/or cellulose that arepredominately not solubilized by NT microbes. These materials are notsolubilized or are only partially solubilized, leaving a major portionas non-solubilized material that is not available to conversion tobiogas. As discussed above, attempts to make these materials availableto NT microbes often involve, for example, chemical and mechanicaltreatment, which is not necessary in the ASB tank 208 according toprinciples described herein.

Contents introduced into the ASB tank 208 having lignocellulosic biomassmay include at least one of animal waste, human waste (e.g., biosolids,etc.), fats, oils, and grease (FOG); food waste/garbage, organic matter,plant matter (e.g., green waste, bio-energy crops, coconut husk, grass,etc.), waste activated sludge (WAS), and algae (e.g. algae grown inreactors, etc.), as well as other contents that may be digested andsolubilized. Note that lignocellulosic biomass and other types of rawmaterial or feedstock may be introduced into the ASB tank 208 beingpre-mixed together (e.g. in the mixing tank 202, previously mixed beforeentering the mixing tank 202, mixed before entering the ASB tank 208,etc.) or added separately.

Besides lignocellulosic biomass, biomass effluent 209 contents mayinclude non-lignocellulose biomass and waste paper that does not havelignin, such as slaughterhouse waste, bacteria cell walls that aresluffed off from a ruminant animal, waste activated sludge (WAS), algae,king's grass, waste paper, etc.

While anaerobic digestion by itself is effective, for example, onhemicellulose side chains, other chains like long cellulose chains areonly slowly digested by anaerobic bacteria, and polyphenols like ligninare resistant or toxic to many microorganisms. The ASB tank 208 canaccess the chains and compounds inaccessible to prior art systems tosolubilize the long cellulose chains and polyphenols. The use ofthermophilic microbes solubilize biomass, up to 90% or more oflignocellulosic materials, making the carbon in the biomass accessiblefor anaerobic digestion.

The ASB tank 208 includes thermophiles that solubilize lignocelluloseand other difficult to digest contents to produce products suitable foranaerobic digestion. The ASB tank 208 further includes at least a basicbicarbonate or other bicarbonate to promote production of biomassproducts suitable for the AD tank 212 and lower the concentration oflactic and acetic acids in the biomass products. The ASB tank 208relationship with the AD tank 212 can be likened to a stomach to anintestine, both the ASB tank 208 and a stomach enhancing breakdown ofcontents for additional processing in the AD tank 212 and intestine. Thethermophilic microbes in the ASB tank 208 can readily digest thesematerials under the thermophilic conditions.

The result is a biomass where a major portion of the lignocellulosicmaterials are converted (e.g., solubilized, metabolized, etc.) to atleast one of lactic acid and acetic acid, which are then readilyconverted to biogas. In an example, the thermophilic anaerobic microbeis C. bescii or another bacteria. Possible other bacteria candidates forthe ASB tank 208 include bacteria of at least one of the genusCaldicellulosiruptor, Clostridium thermocellum, andThermoanaerobacterium saccharolyticum, and other bacteria withcomparable or otherwise suitable properties for digesting at least onelignocellulosic material.

In another example, at least one of fungi, archaea, cellular organism,and an organism or mixture of organisms with comparable or otherwisesuitable properties for digesting a lignocellulosic material is used.

At least one of the bacteria or other examples listed as candidates maybe in a genetically modified form. In another example, at least one ofthe bacteria or other examples listed is found in at least one of a hotspring, a concentration of rotting wood, and a lignocellulose-degradingextremophile. The ASB tank 208 may find further use in medicalindustries. Viruses like those for flu and COVID-19 are inactivatedthrough the ASB treatment. In an example, the virus is subject to two tothree days at a temperature of 75° C.

The thermophilic anaerobic bacteria are adapted to derive energy fromorganic materials that happen to exist in the thermal pools, which areoften the unsolubilized remains of wood. It has been found that thelignin/cellulosic materials in biomass can be digested by these samemicrobes in an industrial scale process that shows dramatically improvedconversion of biomass to biogas, both in terms of short treatment times,and the high portion of biomass converted.

Unlike a system in which various compounds are metabolized in anoxygen-free environment, ASB conditions and microbes are chosen totarget normally inaccessible ligneous and cellulosic portions of thebiomass compounds. The contents in the ASB tank 208 are heated to becomeenvironmentally suitable for thermophile, i.e., thermophilic microbialaction. Under these conditions, the contents introduced to the ASB tank208 are pasteurized, eliminating a substantial portion of, or all of,the microbes except for thermophilic bacteria that survive and thriveunder ASB heated conditions. This culture of thermophilic bacteriadigests lignocellulosic materials, including materials previouslyinaccessible to other anaerobic digestion and creates an enhanced feedfor the anaerobic digestion tank.

For the thermophile to thrive, consideration is taken for a desirabletemperature. During the digestion process within the ASB tank 208, theASB tank 208 is maintained at a desired temperature to provide asuitable environment for the C. bescii or other microbes to solubilizecellulose. An example temperature maintained may include 75° C. orapproximately 75° C. In another example, a temperature range ismaintained, for example, between 45-65° C., or 45-85° C. Narrower rangesinclude 45-50° C., 50-55° C., 55-60° C., 60-65° C., 65-70° C., 70-75°C., 75-80° C., 80-85° C., 60-70° C., 70-80° C., 70-85° C., or 60-85° C.,or other ranges that are used for pasteurization of conventionalanaerobic microbes and growth of ASB thermophilic anaerobic microbes.The higher temperature causes the reactions within the ASB tank 208 togo faster than non-thermophilic temperatures and can be done withoutkilling ASB thermophilic anaerobic microbes, enzymes, and othermicrobes.

The ASB tank 208 is heated to maintain the temperature using anysuitable means. Heat may be suitably recycled from other environmentsdescribed herein as well as other environments and other processes, suchas waste heat from engines and other mechanical devices, exhaust,combustion gas heat, solar, etc.

Another condition that is considered for the ASB tank 208 is the oxygenlimit. The ASB tank 208 is configured to adhere to oxygen limits for C.bescii, based on C. bescii being a strict anaerobe, which is pO₂=0.5%.The ASB may further be configured for higher oxygen levels. For example,C. bescii is capable to withstand oxygen levels as high as pO₂=20% for15-20 minutes. In an example, oxygen levels are thus maintained up to20% for this duration of time.

Another condition for the ASB tank 208 is a suitable pH that should bemaintained for the ASB bacterial growth, such as a range between 4.5 to8.5. For optimal growth of C. bescii, the pH should be controlledbetween 6.5 and 8.5, or 6.8 and 7.2. Lower pH values do not immediatelykill bacteria, but slowly starve it because it cannot acquire energy bymetabolizing sugars from dissolved cellulose. Dissolution of thecellulose also stops because the products are not being metabolized.

In an example, the pH of the ASB tank 208 is controlled. In an example,a base is introduced for pH control and promotion of metabolism. Inanother example, a sufficient base is maintained to react with acidsproduced during metabolism. In another example, bicarbonate (e.g.,HCO₃—, etc.) is introduced or recycled from at least one of the AD tank208 and other environments described herein to control pH of the ASBtank 208. Metabolism and growth of C. bescii are driven by production ofCO₂ gas or water. A base that does not produce sufficient Gibbs energyupon reaction with acids will not provide the energy required foroptimum growth of the bacteria. Thus, an example includes that the basehave a sufficient Gibbs energy to provide the energy needed for optimumgrowth.

Another condition for the ASB tank 208 is the alkalinity, or the amountof base to resist changes in pH that would make the contents moreacidic. The base to be controlled within the ASB tank 208 may includecarbonate and bicarbonate. In an example, bicarbonate is produced by theAD tank 212 and recycled to the ASB tank 208 to maintain a desiredalkalinity or range of alkalinity.

C. bescii is believed to not form a biofilm on biomass particles.Instead, it produces a secretome with exozymes that catalyze dissolutionof the lignocellulosic materials. In an example, the ASB tank 208 mixesthe contents for C. bescii to increase contact between bacteria andbiomass and support the production of exozymes that dissolve thelignocellulosic materials. An example mixing system includes a slow orlow-level mechanical stirring or other suitable system for mixing. Meansfor mixing the contents may include one or more of a plurality ofpaddles and pumps 246.

ASB treatment examples include at least one of a batch process,semi-continuous process, and a continuous process. The reaction in theASB tank 208 may depend on the time period depending on the feedstockand desired level of material destruction. In an example, ASBcontainment for reaction includes a period of time between 0 to 48hours. In another example, the period of time is 0 to 7 days. The timefor a reaction using C. bescii may be between 0.5 hour to 200 hours, butmore typically 12-72 hours. C. bescii is suitable because it can rapidlydepolymerize and solubilize lignocellulosic (plant material) and othercellular material. C. bescii further produces exozymes that catalyzehydrolysis of cellulose and lignin at a rapid rate. In an example, theproducts are sugars and phenolic compounds from lignin that aremetabolized to acetic acid and lactic acid by C. bescii as a source ofGibbs energy for growth and activity.

In an example, at least a portion of the treated biomass and a portionof the biomass products are provided to the AD tank 212. To meet theconditions of the AD tank 212, the ASB effluent 210 may be cooled, forexample, by a cooling reservoir or heat exchange system, prior toentering the AD tank 212 or other location.

ASB Treatment Reactions with C. bescii Include:

Lignocellulose→(acetate+lactate) ions+CO₂(g)+oxygenated aromatics fromlignin+residual sugars. These reactions are catalyzed by exozymesproduced by C. bescii. During treatment in the ASB tank 208, acetic andlactic acids in the presence of bicarbonate react to produce acetateion, lactate ion, and CO₂ gas. Acetic and lactic acids react with basein the pH buffer to produce acetate ion, lactate ion, and CO₂ gas. Therate of ASB treatment can be obtained by monitoring the increase in CO₂gas pressure over the ASB treatment mixture in a sealed vessel or by oneor more of measurement of the change in total suspended solids andvolatile solids as ASB treatment progresses. Products are not toxic toanaerobic digestion microorganisms and are rapidly digested in the ADtank 208 to produce biogas.

ASB Treatment Metabolic Reactions Include:

Sugars→acetic acid+lactic acid. For this reaction to occur at asignificant rate, the concentration of acetic and lactic acid must bekept low by reaction with bicarbonate or another base.

Acetic acid+bicarbonate→acetate ion+CO₂+H₂O. The Acetate/Lactate ionsand residual sugars are rapidly metabolized in the AD by anaerobicbacteria, producing CO₂, and CH₄, as follows;

Acetate/Lactate ions+sugars→methane+CO₂+bicarbonate (which may berecycled back to the ASB tank 208).

At least one bacterial organism used in the ASB tank 208 can beintroduced by any suitable method, and conditions should be maintainedfor optimum growth. For example, trace elements, nutrients, vitamins,and the like may be introduced to start or maintain the ASB treatmentprocess.

For C. bescii, specific optimum conditions have been shown to includethe following: 78° C., DSMZ media (0.33 g NH₄Cl, 0.33 g KH₂PO₄, 0.33 gKCl, 0.33 g MgCl₂*6 H2O, 0.33 g CaCl₂*2 H₂O, 0.50 g Yeast Extract, 0.50mL Na-resazurin solution (0.1% w/v), 1.50 g NaHCO₃, 0.50 g Na₂S*9 H₂O,1.00 mL of a trace element solution, 10.00 mL of a vitamin solution to1000.00 mL distilled water.

The trace element solution (designated SL-10) was, in an example,composed of 10.00 mL HCl (25%; 7.7 M), 1.50 g FeCl₂*4 H2O, 70.00 mgZnCL₂, 100.00 mg MnCl₂*4 H₂O, 6.00 mg H₃BO₃, 190.00 mg CoCl₂*6 H₂O, 2.00mg CuCl₂*2 H₂O, 24.00 mg NiCl₂*6 H₂O, 36.00 mg Na₂MoO₄*2 H₂O, and 990.00mL Distilled water. The FeCl₂ was dissolved in the HCl, which was thendiluted in water. The remaining salts were added and the solution wasdiluted to 1000.0 mL. The vitamin solution was composed of 2.00 mgBiotin, 2.00 mg Folic acid, 10.00 mg Pyridoxine-HCl, 5.00 mgThiamine-HCL*2 H2O, 5.00 mg Riboflavin, 5.00 mg Nicotinic acid, 5.00 mgD-Ca-pantothenate, 0.10 mg Vitamin B12, 5.00 mg Lipoic Acid, and 1000.00mL Distilled water. The solutions should be stored under anaerobicconditions.

In prior art processes, a great expense may be involved in hauling awayand safely disposing of waste material. The ASB tank 208 and othercomponents described herein have great market potential because of theincrease in quantity of commercially viable product that they yield overcurrent methods. This reduces undigested waste material.

Another advantage in using the ASB tank 208 and other components is thatthey yield 1.5 to 10 times as much gas than if biomass is put directlyinto an AD tank 212.

AD Tank

After the ASB tank 208, at least a portion of the ASB treated biomass210 enters the AD tank 212. Compared to conventional feed streams of ananaerobic digester, the ASB treated biomass 210 is more available foranaerobic metabolism and digestion than typical biomass feeds toanaerobic digestion. In particular, an advantage of extremelythermophilic ASB treatment is its pasteurization of the biomass 209before being introduced into the AD tank 212, thus allowing bettercontrol of the AD microbes and processing.

For acetate only ASB effluent 210, CO₂ may still be present in thebiogas from digestion within the AD tank 212. It is speculated that suchCO₂ in the biogas may come from compounds other than acetate that wereproduced in the ASB tank 208.

Within the AD tank 212 are maintained suitable bacteria and archaea,such as acetogens and methanogens, that support production of biogas.Methanogens grow better with the ASB treated biomass 210 from the ASBtank 208 than with conventional untreated biomass. In an example, the ADtank 212 includes at least one of anaerobic bacteria and archaea toconvert the treated biomass 210 into biogas under anaerobic digestiveconditions. In another example, a portion of the AD treated biomass 211is recycled back to the ASB tank 208 as indicated by the black arrow.The portion of AD treated biomass 211 may include, for example, basicbicarbonate or other bicarbonate produced within the AD tank 212 thatmay be recycled to control pH and promote metabolism with the ASB tank208.

In other examples, at least one of the AD tank 212 and an AD satellitereservoir 236 provides the basic bicarbonate or other bicarbonate to theASB tank 208. In an example, the bicarbonate is taken after AD treatmentand can be a specified amount as needed or desired. In an example, theAD tank 212 is preferred for drawing bicarbonate with the AD satellitereservoir 236 being a back up resource.

Conditions in the AD tank 212 are maintained to allow anaerobic bacteriato thrive. An example temperature includes 40° C. Further examplesinclude a temperature range between 15° C. to 85° C. The pH of the ADtank 212 may range from 6.5 to 8.5, with more narrow ranges including6.5-7, 7-0.7.5, 7.5-8, or 8-8.5. In an example, the pH of the AD tank212 is maintained at 7 or slightly below 7 (e.g, 6.5-6.6, 6.6-6.7,6.7-6.8, 6.8-6.9, 6.9-7, etc.). In another example, the temperature andpH are substantially different from the temperature and pH in the ASBtank 208. Maintaining disparate conditions where an organism of the ASBtank 208 and the bacteria in the AD tank 212 can thrive is at least onereason that separate tanks or digesters are provided for each part ofthe treatment.

The AD tank 212 may include at least one of a continuous stir, up flowanaerobic sludge blanket, induced bed reactor, dual anaerobic/aerobicdigester, or any kind of anaerobic digester for the reaction. Treatmentmay be at least one of a batch process, semi-continuous process, and acontinuous process.

In an example, the ASB tank 208 has a volume ratio with the AD tank 212between 1:10 to 10:1 as defined by a relative rate of degradation of thebiomass in the ASB tank 208 to the production of biogas in the AD tank212.

In an example, the AD tank 212 has two main product streams includingprincipally gas and liquid phase streams. The first main output stream(1), or biogas stream, contains at least one of methane (CH₄) and carbondioxide (CO₂), but may also contain other reaction products andimpurities (e.g., H₂S, and H₂O). The biogas stream is directed tosuitable gas processing for its intended use. Bicarbonate is recycledback to the ASB tank 208. The second main output stream (2) is a slurryof undigested waste (dead bacteria, inorganic portions, dirt, etc) thathas been pasteurized, and which therefore can be processed as a soilconditioner or compost. In an example, there is no biomass left. Becausethe biogas stream is considered to be pathogen free, pasteurizationproduces a higher quality, more valuable undigested waste thanconventional AD treatment.

Reactions in the AD tank include:(Acetate) CH₃COO⁻ _((aq))→CH_(4(g))+HCO₃ ⁻ _((aq))(Lactate) 2 CH₃CH(OH)COO⁻ _((aq))+H₂O→3 CH_(4(g))+2 HCO₃ ⁻_((aq))+CO_(2(g))(Sugars) 2C₁H₂O→CH_(4(g))+CO_(2(g)),

Production of acetate in the ASB tank 208 uses one bicarbonate anddigestion of acetate produces one bicarbonate in the AD tank 212.Production of lactate uses one bicarbonate and digestion of lactateproduces one bicarbonate ion. Thus, the reactions in the AD tank 212produce the same amount of bicarbonate as the amount used in treatmentin the ASB tank 208. Balancing bicarbonate (i.e. acid/base balance)would require recycling 100% of the biomass effluent from the AD tank212. Efficiency of that nature is unlikely to be possible and notpractical. Instead, bicarbonate may be introduced to the ASB tank 208 orthe mixing tank 202 from other sources, or by adding another base to theASB tank, such as ammonia, sodium carbonate, sodium bicarbonate,potassium hydroxide, and sodium hydroxide.

An application of ASB/AD digestion system will include optional systemsdesigned to exploit the advantages of the ASB/AD system, and provide asuitable industrial operating environment. Below is a fuller descriptionof exemplary systems.

Treating biomass with the ASB prior to anaerobic digestion is effectivein promoting anaerobic digestion and does not introduce any harmfulchemicals or otherwise harm the environment for the anaerobic bacteriain the AD tank 212 where biogas is produced. Note that C. bescii andother thermophiles are not considered to be pathogens because theycannot survive at low or mesophilic temperatures.

Mixing Tank

A mixing tank may be used to treat biomass before entering the ASB tank212. The mixing tank 202 includes treatment that is to create afeedstock, or biomass effluent 209, for the ASB tank 212 that issuitable for and that promotes growth of the thermophilic microbes ofthe ASB tank 208. The mixing tank 202 may mix biomass with water, andpossibly other reagents as well. In addition, the mixing tank 202 mayheat the biomass 258. Mixing the biomass 258, or mixing and heating ofthe biomass 258 with water, may occur before treating the biomass 258 inthe ASB tank 208 to mitigate pH changes and promote metabolism. Also,the mixing tank 202 may be used to remove oxygen from the biomass 258and promote hydrolysis of biomass solids. In an example, the mixing andheating occurs prior to entry to the mixing tank 202.

Contents introduced to the mixing tank 202 having lignocellulosicbiomass may include the same types of materials that enter the ASB tank208, namely, at least one of animal waste (e.g. manure, etc.); humanwaste (e.g., biosolids, etc.); fats, oils, and grease (FOG); foodwaste/garbage; organic matter; plant matter (e.g., green waste,bio-energy crops, coconut husk, grass, etc.); waste activated sludge(WAS); and algae (e.g., algae grown in reactors, etc.), as well as othercontents. Lignocellulosic biomass along with other types of raw materialor feedstock may be introduced into the mixing tank being premixedtogether or added separately. Besides lignocellulosic biomass, biomass258 contents may include non-lignocellulose biomass and waste paper thatdoes not have lignin, such as slaughterhouse waste and waste paper.

Once the biomass 258 is treated with at least one of water, heat, andmixing, etc., the biomass effluent 209 from the mixing tank 202 is atreated biomass for the ASB tank 208 rather than its original form ofbiomass 258.

An example treatment includes the biomass 258 being ground to a 3 cmparticle size and then being supplied to the mixing tank 202 beforebeing introduced to the ASB tank 208. The contents of the mixing tank202 are adjusted to a composition that is approximately 2% to 50% (e.g,6% has been found suitable), and heated to approximately 60° C. to 100°C. for 1 to 6 hours. During this period of time, mixing can beaccomplished, for example, with one or more of a plurality of paddles244 and/or pumps. This process has the effect of pasteurizing thecontents, expelling dissolved O₂, and providing the contents with anoptimal temperature for thermophilic microbial action.

The resultant biomass effluent 209 produced by the mixing tank 202 issent to the ASB tank 208 in the form of a liquid suspension, slurry, ormash of solids. An example solids content of the effluent may representapproximately 10% of the effluent.

In an example, a solution or “tea” containing soluble materials in thebiomass 258 or treated biomass 209 is separated from the solids contentand sent directly to an AD tank 212. In another example, the biomass 258is mixed with water to suspend at least a portion of the biomass 258 inthe water and partially solubilize components of the biomass 258. Inanother example, the biomass effluent 209 includes at least a portion ofone of suspended biomass and partially solubilized components of biomassbeing transferred to the ASB tank 208.

For some types of biomass, raw material, and feedstocks, the mixing tank202 can also serve as a hydration tank in which hydration is provided.Also, two separate tanks are contemplated, one tank for hydration andone tank for mixing.

ASB Satellite Reservoir

Satellite reservoirs may be provided that are associated with at leastone of the tanks or environments, according to principles discussedherein. In an example, the ASB tank 208 benefits from a connection to aseparate, independent ASB satellite reservoir 236. For example, theremay be times when the ASB tank 208 becomes compromised due to areinoculation failure. There may also be a bacterial, cultural, enoculumwashout in which there is too short of a mean resonance time whichpushes material out before bacteria grows. As a result, the wholecommunity becomes washed out because the bacteria cannot grow fastenough. In another example, toxins and antiobiotics in the biomass arepresent. There may also be a chemical restrictions of the feedstockpresented, or other problem. To counter occurrences of this nature andprevent failure of the ASB tank 208, an ASB satellite reservoir 236 asshown in FIG. 1 efficiently maintains and provides at least one of abacteria, nutrient, or other matter to the ASB tank 208 as needed ordesired to promote digestion of the biomass effluent 209. The satellitereservoir 236 may be provided with an environment to, for example,provide inoculation, assist in maintaining a condition, assist instartup, or introduce/maintain a precultured microbe culture, a chemicalagent, micronutrient, or the like. Any storage or auxiliary processingthat can be maintained separately from the main environment and thatenhances the main environment is contemplated. Satellite reservoirs canbe particularly useful when applied to an ASB environment and an ADenvironment.

In addition, the ASB satellite reservoir 236 may also be used for atleast one of the following—1) maintaining bacteria culture suited forthe ASB tank 208, 2) alleviating the need for trace elements to be addedto the ASB tank 208, depending on feedstock chemical characteristics, 3)adapting or conditioning C. bescii to utilize the feedstock present inthe ASB tank 208, 4) speeding up the ASB treatment process in the ASBtank 208 by avoiding time that otherwise would be required for the C.bescii to grow in the ASB tank 208, and 5) adding a base, such asbicarbonate, to the ASB tank 208 to maintain pH and support metabolism.

In an example, the ASB satellite reservoir 236 facilitates thecontinuous inoculum of C. bescii. In addition, the satellite reservoir236 contains nutrients necessary for C. bescii growth and a small amountof the ASB treatment feedstock (e.g., biosolids, green waste, energycrops, food waste, raw or organic materials, etc.). The C. bescii orother matter in the satellite reservoir is maintained at or near 1×10⁶cells per milliliter density.

Bacteria besides C. bescii that may be maintained in the ASB satellitereservoir 236 includes one or more of Caldicellulosiruptor bescii,Caldicellulosiruptor genus, Clostridium thermocellum,Thermoanaerobacterium saccharolyticum. Note that bacteria in the ASBsatellite reservoir 236 is maintained at a pH range of 6.5-7, 7-0.7.5,7.5-8, 8-8.5, 6.5-7.5, 7.5-8.5, or 6.5-8.5. Additionally, the bacteriamay be cultured separately before being added to the ASB satellitereservoir 236.

In an example, the ASB satellite reservoir 236 maintains at least one ofbacteria and archaea to be fed to the ASB tank 208. The ASB satellitereservoir 236 may maintain at least one of the following—a nutrient forbacterial growth, food waste, animal manure, biosolids, waste organicmaterial, sewage, garbage, waste activated sludge, FOG, waste paper,lignocellulosic plant materials, and cellular material.

In addition to bacteria and nutrients, at least one of a trace nutrientand trace element may be maintained in the ASB satellite reservoir 236.In an example, at least one of a trace nutrient and trace element aremaintained that is necessary for a bacteria in the ASB tank 208 to growand divide. In another example, at least one of a trace nutrient andtrace element are maintained to overcome a chemical restriction of thefeedstock in the ASB tank 208. In operations that include C. bescii, atleast one additional nutrient and trace metal may be provided to furtherfacilitate C. bescii growth. Exemplary trace elements and proportionateamounts to obtain 1000 mL are shown in Table C below.

TABLE C Trace element solution SL-10: HCl (25%; 7.7M) 10.00 ml FeCl₂ × 4H₂O 1.50 g ZnCl₂ 70.00 mg MnCl₂ × 4 H₂O 100.00 mg H₃BO₃ 6.00 mg CoCl₂ ×6 H₂O 190.00 mg CuCl₂ × 2 H₂O 2.00 mg NiCl₂ × 6 H₂O 24.00 mg Na₂MoO₄ × 2H₂O 36.00 mg Distilled water 990.00 ml First dissolve FeCl₂ in the HCl,then dilute in water, add and dissolve the other salts. Finally make upto 1000.0 ml.

In addition, a sucrose or a carbon source may be maintained in the ASBsatellite reactor 236 to promote optimal conditions for bacteria to growand thrive and ultimately produce enzymes that will benefit the contentsof the ASB tank 208. Also, a yeast, such as brewer's yeast, may be addedto the ASB satellite reservoir 236 to promote growth of the bacteria byproviding needed amino acids. An example sample of nutrients per litermaintained in the ASB satellite reservoir 236 include glucose (1 g),yeast extract (0.1 g) (e.g., brewer's yeast or another source of aminoacids, etc.), NH₄Cl (0.05 g), KH₂PO₄ (0.05 g), MgCl₂ (0.05 g), CaCl₂(0.05 g), NaHCO₃ (1.0 g), and Na₂S (0.1 g to ensure anaerobicconditions). Note that the ASB satellite reservoir 236 may provide onespecific type of content or a combination of at least one of a bacteria,nutrient, trace nutrient, trace element, sucrose, carbon matter, andother matter.

In an example, the contents in the ASB satellite reservoir 236 are grownon a substrate or other contents that are the same or similar to thebiomass in the ASB tank 208. For example, if the biomass within the ASBtank 208 contains manure, the contents within the ASB satellitereservoir 236 are grown on manure or contents that include manure. Ifsludge is in the biomass, sludge is used as the substrate or as part ofthe substrate within the ASB satellite reservoir 236.

The similar contents enable similar bacterial propagation between thetwo environments. If the contents in the ASB satellite reservoir 236 areonly given one type of biomass, the contents will have a difficult timebeing able to break down foreign types of biomass that are present inthe ASB tank 208. The reason for this is that bacteria will not makeenzymes that are not needed. For example, growing bacteria with onlysucrose in the ASB satellite reservoir 236 will shut down genes that arenot needed to metabolize sucrose. Introducing the sucrose fed bacteriainto an ASB tank 208 that contains grass clippings will make thebacteria unable to break down the grass clippings because the bacteriawere conditioned to metabolize sucrose. Maintaining similar conditionsof bacteria and biomass between the ASB tank 208 and the ASB satellitereservoir 236 is therefore a support to the system as a whole.

In an example, the substrate comprises at least one of biomass effluent209 from the mixing tank 202, ASB effluent 210 from the ASB tank 208, ADtreated biomass 240 from the AD tank 212, nutrient for growth, foodwaste, human waste, animal manure (animal waste), biosolids, wasteorganic material, sewage, garbage, waste activated sludge, algae, FOG,organic matter, plant matter, waste paper, lignocellulosic plantmaterials, and cellular material. In addition to the substrate, the ASBsatellite reservoir 236 may contain, for example, at least oneacetoclastic methanogen.

Additional conditions of the ASB satellite reservoir 236 may by close oridentical to that of the ASB tank. In an example, oxygen levels withinthe ASB satellite reservoir 236 are the same as, or similar to, theoxygen levels as the ASB tank 206. In another example, the ASB satellitereservoir 236 is configured to adhere to the oxygen limits for C.bescii, based on C. bescii being a strict anaerobe, which is pO₂=0.5%.The satellite reservoir 236 may further be configured for higher oxygenlevels, such as pO₂=2% for 15-20 minutes. Maintaining a same oxygenlevel or maintaining certain oxygen levels for at least one or morespecific constraint, such as a given set of contents and for certaintime durations, may support the growth rates desired of the system.

Another condition of the ASB satellite reservoir 236 that may be closeor identical to that of the ASB tank 206 is temperature. This may be aconstraint that helps the ASB satellite reservoir 236 to stay inoculatedwith a particular bacteria that is suited for the ASB tank 206.Furthermore, maintaining a specific temperature or temperature range mayenable the ASB satellite reservoir 236 to stay inoculated with aparticular bacteria that is suited for the ASB tank 206. Temperatureranges that are maintained and that may be the same or similar to thetemperature ranges of the ASB tank 206 may include, for example, 60-65°C., 65-70° C., 70-75° C., 75-80° C., 80-85° C., 60-70° C., 70-80° C.,70-85° C., or 60-85° C. degrees. Furthermore, temperature changes may beminimized during transport of contents from the ASB satellite reservoir236 to the ASB tank 206 to protect the state of the bacteria or othermatter.

Specific volume ratios or a range of volume ratios may also be observedbetween the ASB satellite reservoir 236 and the ASB tank 206. In anexample, the satellite reservoir 236 has a volume ratio to the ASB tank206 within a range of 1:10 to 10:1. In another example, the volume ofthe ASB satellite reservoir 236 is approximately 1/100 the volume of theASB tank 206, or within a range of 1/200 to ½ of the volume of the ASBtank 206. In terms of mass per volume, the ASB satellite reservoir 236may contain 0.5-1.0% of the ASB treated biomass. The volume ratios andpercentages may be used to control and predict behavior of the contentswithin the ASB satellite reservoir 236 and the ASB tank 206.

In an example, the ASB satellite reservoir 236 provides at least one ofa bacteria, nutrient, or other matter, primarily at two different times.The first time is at or near the beginning of the ASB treatment. Thesecond time occurs when trace nutrients are depleted and not provided bythe feedstock.

In another example, feeds to the ASB tank 206 occur at various times andin a manner so as to maintain an exponential growth culture. The meandoubling times for various feedstocks with C. bescii are shown in TableA1 below to provide information on the way to feed the ASB tank 206 soas to maintain their exponential growth culture. C. bescii growing onstarch, for example, has a mean doubling time of 2.1 hours andtherefore, quantities of the starch within the ASB tank 206 may be fedwith contents in the ASB satellite reservoir 236 to double the amount ofstarch within that time frame.

TABLE A1 C. bescii Mean Feedstock Doubling Time (hours) Starch 2.1Newspaper 4.6 Barley Shoots 3.6 Kentucky Blue Grass lawn clippings 3.4Switchgrass 2.3 Poplar twigs 2.4 Corn Husk 4.3 Feedstock and the meandoubling time with C. bescii

If a feedstock lacks the necessary requirements for C. bescii growth,contents from the ASB satellite reservoir 236 may provide specificchemical constituents to maintain such growth. For example, the C:N:Pratio of 500:10:1 dictates the addition of major nutrients, N and P, asNH₄Cl, yeast extract, and/or KH₂PO₄.

An example ASB satellite reservoir 236 includes a monitoring system ordevice that monitors at least one of pH level, oxygen content, and typeof bacteria present within the reactor. The monitoring system or asecond monitoring system may further monitor at least one of the ASBtank 208 and AD tank 212. A delivery system manually, automatically, orsemi-automatically delivers contents from the ASB satellite reservoir tothe ASB tank 208 in quantities that are determined to be needed for theASB tank 208. In an example, chemical analysis is performed so thattrace metals that are lacking in the ASB tank 208 may be added includingat least one of Fe, Zn, Mn, B, Co Cu, and Ni. In another example,product formation of acetate, lactate, oxygenated aromatic compounds,etc., is also monitored. The ASB satellite reservoir 236 may requirethat its entire volume be replaced every 72 hours or within a range of50-80 hours.

AD Satellite Reservoir

Like the ASB tank 206, a separate, independent satellite reservoir maybe connected to the AD tank 212. This is shown in FIG. 2 in which anexample reactor includes an AD satellite reservoir 437 attached to an ADtank 412. The rest of the reactor may remain the same as FIG. 1, with amixing tank 202, ASB tank 208, ASB satellite reservoir 236, and variouscomponents therein.

In FIG. 2, biomass 458 is supplied to the mixing tank 402 for mixing bymixing paddles 444 as powered by mixing motor 426. Biomass effluent 409that is produced in the mixing tank 402 is supplied as indicated by ablack arrow to the ASB tank 408. ASB treatment within the ASB tank 408may include mixing by mixing paddles 446 and heat. The ASB tank 408 maybe powered by the ASB motor 432.

In an example, the ASB satellite reservoir 436 is used to supply one ormore of a bacteria, nutrient, or other matter to the ASB tank 408. Thecontents within the ASB satellite reservoir 436 may be mixed by mixingpaddles 448 and heated. The ASB satellite reservoir 436 may be poweredby the ASB motor 434.

ASB treated biomass 410 that is produced by the ASB tank 408 is suppliedto the AD tank 412, as indicated by a black arrow, for anaerobicdigestion. The AD tank 412 includes mixing by mixing paddles 447 andheating capabilities to treat the contents therein, as powered by ADmotor 438. In an example, at least a portion of the contents such as CO₂and bicarbonate 411 that are produced within the AD tank 412 arerecycled back to the ASB tank 408, as indicated by a black arrow, orused for other purposes.

The AD satellite reservoir 437 is used to supply additional contents tothe AD tank 412. The contents within the AD satellite reservoir 437 maybe mixed by mixing paddles 449 and heated. The AD satellite reservoir437 may be powered by an AD satellite motor 439. In an example, the ADsatellite reservoir 437 contains at least one of the contents found inthe AD tank 412. In another example, the AD satellite reservoir 437contains substantially similar or identical content as found in the ADtank 412. In another example, at least one of archaea, acetoclasticconsortium, and other matter is provided to the AD tank 412. In anexample, the AD satellite reservoir 437 incubates bacteria that is usedto augment desired bacteria in the AD tank 412 for processing of the ASBtreated biomass in the AD tank 412. In another example, the AD satellitereservoir 437 maintains at least one of bacteria and archaea that areused to augment at least one bacteria and archaea in the AD tank 412. Ina further example, the AD tank 412 is augmented from the AD satellitereservoir 437 with at least one of archaea and acetoclastic consortiumisolated from WAS. In another example, the AD satellite reservoir 437augments bacteria in the AD tank 412 that are specific to biogasproduction from the molecules being produced in the ASB tank 408. Inanother example, the AD satellite reservoir 437 supplies one or more ofa nutrient solution and base to the AD tank 412.

The AD tank 412 may contain at least one of a synthetic content orbiogenetically engineered content which are bio-augmented. The ADsatellite reservoir 437 may also contain respective synthetic contentsor biogenetically engineered contents.

Bioaugmentation with archaea has shown a significant reduction ofacetate accumulation within seven days and the proportion of methane inbiogas increased almost over a hundred-fold (Town and Dumonceaux, 2015).In an example, at least one of archaea and acetoclastic consortium isisolated during multiple successful digestions of WAS when methaneproduction is relatively high to increase the likelihood that thearchaea will thrive within similar AD conditions. The archaea oracetoclastic consortium may be cultured with DSMZ Medium 141 to capturelocal methanogens and an additional consortium is created that is spikedwith two well-known Methanosarcina, Methanosarcina barkeri, DSMZ 800,and Methanosarcina acetivorans DSMZ 2834.

Consortia may be cultivated continuously at 55° C. for 6 months prior tobioaugmentation experiments in the AD tank and produced with consistentlevels of methane in biogas. In an example, at least one of archaea andacetoclastic consortium may be added to the AD tank by an AD satelliteprior to WAS/AD and periodically to reseed the AD tank when methaneproduction drops.

There may be multiple satellite reservoirs for one tank, eitherduplicate, or with a different content, depending upon the specificcontent or purpose. For example, there may be two satellite tanksassociated with the ASB, one for micronutrients, and another for C.bescii. In another example, there may be three types of satellitereservoirs, including at least one to deliver the bacteria, at least oneto provide nutrients, and at least one to provide microbes, such asthermophilic microbes (C. bescii) for the ASB or NT microbes from theAD. In another example, nutrients provided by a satellite reactorinclude at least two main types of contents, such as two types ofnutrients or two types of trace metals. In another example, thesatellite reactor provides a combination of types of contents, such asat least one type of nutrient and at least one type of trace metal.

An example of a reactor system includes at least three satellitereservoirs that supply contents to the ASB and AD tanks, each satellitereservoir providing same or different contents at same or differenttimes and rates. The first satellite reservoir is for the ASB tank andincludes C. bescii, the second satellite reservoir is for the AD tankand includes at least one of archaea and acetoclastic bacteria, and thethird satellite reservoir for the AD tank includes oxidativemethanogenic bacteria. In another example, a specific type of bacteria,either the archaea, acetoclastic bacteria, or the oxidative bacteria, isdelivered to the AD tank. In another example, predetermined quantitiesof bacteria from each tank are delivered to the AD tank. Furtherexamples include that controls over at least one of an amount, time, orrate depends on determinations made by a monitoring process or otherprocess.

In an example, the AD satellite reservoir contains bacteria grown on asubstrate that is close or identical to effluent from the ASB tank. Thecontents may be grown on a substrate or other contents that are close oridentical to the biomass effluent 409 in the ASB tank 408. In anexample, the substrate comprises at least one of biomass effluent 409received from the ASB tank 408, nutrient for growth, food waste, humanwaste, animal manure (animal waste), biosolids, waste organic material,sewage, garbage, WAS, algae, FOG, organic matter, plant matter, wastepaper, lignocellulosic plant materials, and cellular material. Inaddition to the substrate, the AD satellite reservoir 437 may contain,for example, at least one of acetoclastic methanogen and archaea.

At least one condition of the AD satellite reservoir 437 may be close oridentical to at least one of the AD tank 412 or other environment. Suchconditions may include, for example, oxygen levels, temperature, volumeratios, and ranges thereof.

Maintaining a specific temperature or temperature range may enable theAD satellite reservoir 437 to stay inoculated with a particular bacteriathat is suited for the AD tank 412. Temperature ranges that aremaintained and that may be the same or similar to the temperature rangesof the AD tank 412 may include, for example, 60-65° C., 65-70° C.,70-75° C., 75-80° C., 80-85° C., 60-70° C., 70-80° C., 70-85° C., or60-85° C. degrees. Furthermore, temperature changes may be minimizedduring transport of contents from the satellite reservoir to the AD tank412 to protect the state of the contents.

The same or similar type of monitoring processes as the AD tank 412 maybe implemented with the AD satellite reservoir 437, whether themonitoring be the same system or a separate, independent system.

In an example, the AD satellite reservoir 437 has a volume ratio to theAD tank 412 within a range of 1:10 to 10:1 as defined by a relative rateof degradation of the biomass in the ASB tank 408 to the production ofbiogas in the AD tank 412. In another example, the volume of the ADsatellite reservoir 437 is approximately 1/100 or within a range of1/200 to ½ of the volume of the AD tank 412. The volume ratios andpercentages may be used to control and predict behavior of the contentswithin the AD satellite reservoir 437 and the AD tank 412.

Although reference is made specifically to the AD tank 412, the ADsatellite reservoir 437 may supply contents to other environments andits principles may be applicable to other tanks and processes describedherein and are not intended to be limited to the AD tank 412.

Applying these findings, a synthetic microbial community may beincorporated in at least one of the ASB tank 408 and in the AD tank 412.A synthetic microbial community is a systems approach to reducing thecomplexity, while increasing the controllability, by selectinggenetically-engineered or wild type microorganisms that cooperatemetabolically. The combination of different microbial species maydecrease the potential competition between species, often leading to theco-metabolism of a substrate in an independent manner. In the ASB tank408, for example, depending on feedstock, an additional species, such asClostridium thermocellum, may be provided by the ASB satellite reservoir436 or AD satellite reservoir 437 to help decompose difficult to digestbiomass (e.g. lignocellulolytic materials). Also, a synthetic communityof substrate dependent microbes configured specifically to digestacetate and lactate and the products of ASB treatment may be provided bythe AD satellite reservoir 437.

In an example, the ASB tank 408 favors production of acetate ion overlactate ion to produce a reduced CO₂ content in the biogas from the ADtank 412 and to produce increased bicarbonate which may be used in atleast one of the ASB tank 408 and AD tank 412. Please see Section Aentitled EXAMPLE KINETIC MODEL to see a model that shows that ASBtreatment results in ASB effluent with acetate as the major ASBtreatment product.

Biogas Processing

If desired, at least a portion of AD biogas produced in an AD tank maybe used by itself or be subjected to a at least one of a biogasprocessor or conditioner to process or condition biogas suitable for itsintended use. The biogas processor may remove at least one of siloxanes,carbon dioxide, hydrogen sulphide, moisture (e.g. water, etc.), andcontaminants from the AD biogas to make it suitable for at least oneintended use. Further processing is also anticipated with the biogasconditioner.

Turning to FIG. 3, a reactor is shown that includes the use of a biogasprocessor 42 used in conjunction with a mixing tank 19, ASB tank 18, andAD tank 12. As in previous examples, at least a portion of the AD biogas10 goes through a gas processor 4 to be processed. This may involve theremoval of components of the gas or at least one or more chemicalreactions with the AD biogas 10. In a further example, at least aportion of the AD biogas 52 goes through a biogas processor 42 with amore purified gas form resulting. The more purified gas form may bedirected to at least one of a pipeline and an electrical generator. Thisis demonstrated as shown by purified gas from 11 a entering a gasprocessor 5 a to yield methane 50 a, and purified gas from 11 b enteringan electrical generator 5 b to produce electricity 50 b. Note that anexample includes that the gas processor 4 may not be used if a biogasconditioner 42 is present.

In another example, at least a portion of the contents within the biogasprocessor 42 are recycled back or directed back to at least one of themixing tank 19, ASB tank 18, or any other process tank or environment.Recyling lines are showed as dashed lines. The contents may include atleast a portion of the more purified gas form or at least one specificcontent that is separated from the more purified gas form. As shown,contents 53 and 54 are directed to respective mixing tank 19 and the ASBtank 18. Specific contents separated from the more purified gas form mayinclude, for example, at least one of CH₄ and CO₂ or other content thatis used to aid its respective tank in processing its biomass content, asshown, biomass 58 treated within the mixing tank 19 and biomass effluent6 treated within the ASB tank 18.

In another example, CO₂ is recycled to one or more of the mixing tank 19or ASB tank 18. Gas processing requirements may be significantly reducedor eliminated by choice of the ASB bacteria and the processingconditions. As noted elsewhere, lactate in the AD tank 12 is metabolizedto methane (CH₄), bicarbonate (HCO₃ ⁻), and carbon dioxide (CO₂).Acetate is metabolized to methane and bicarbonate. Sugars aremetabolized to methane and carbon dioxide. If carbon dioxide is reducedor eliminated as an AD tank product, gas processing to remove carbondioxide can be correspondingly reduced or eliminated.

An experiment was conducted to test the modification of the bacteriaand/or conditions in the ASB tank for production of only acetate insteadof a mixture of acetate, lactate, and sugars. In an example, acetate isthe feed, and may be the only feed, to the AD tank 12, such thatmodification of the AD bacteria and/or conditions enable the productionof methane with little or no CO₂ in the AD biogas. This eliminates gasprocessing to remove CO₂, which is a costly process. In an example, atleast one of a majority of acetate or only acetate is produced by ASBtreatment with C. bescii.

In an example, the biogas is used to produce power generation. Thisinvolves combustion of the CH4. The combustion gas, which containsmostly nitrogen, but also CO₂, may also advantageously be recycled tothe mixing tank 19 or the ASB tank 18 to displace oxygen or air.

In another example, the biogas is processed and compressed forcompressed natural gas (CNG). It may also be used as a feed stock forchemical processing, such as a Fischer-Tropsch process for production ofbiodiesel or other fuel.

Recycling, Heat Recovery, Purification

To increase process efficiency, reduce material costs, and reduceparasitic losses of material and energy, at least one of heat recovery,recycling, and purification can be employed. In an example, recyclingstreams may be implemented such that at least one environment providesat least a portion of its contents to at least one other environmentbefore, during, or after a digestion related process occurs in thatenvironment. Turning to FIGS. 4-6, black arrows show various paths inwhich content may flow and which may be used to promote at least oneinstance of recycling between at least one environment to at leastanother environment.

FIG. 4 illustrates recycling that may occur within a reactor thatincludes an ASB tank 18, AD tank 12, and biogas processor 4. Recyclinglines are showed as dashed lines. As can be seen, content flow orrecycling may occur in at least one of the following ways—

biogas processor 4 to ASB tank 18 indicated by dashed line 15

AD tank 12 to ASB tank 18 indicated by dashed line 9

FIG. 5 illustrates recycling that may occur within a reactor thatincludes a mixing tank 19, an ASB tank 18, and AD tank 12 in at leastone of the following ways—

biogas processor 4 to ASB tank 18 indicated by dashed line 16

AD tank 12 to ASB tank 18 indicated by dashed line 9

mixing tank 19 to AD tank 12 indicated by dashed line 17

biogas processor 4 to mixing tank 19 indicated by dashed line 47

FIG. 6 illustrates content flow (lines 37 and 27) and recyclingavailable with an ASB satellite reservoir 13 and an AD satellitereservoir 14. Recycling lines are showed as dashed lines. Content flowand recycling may include at least one of the following paths—

the ASB satellite reservoir 13 to (dashed line 23) and from (dashed line24) the mixing tank 19,

the ASB satellite reservoir 13 to (dashed line 33) the ASB tank 18,

the ASB satellite reservoir to 13 to (dashed line 29) and from (dashedline 30) the AD tank 12,

the AD satellite reservoir 14 to (dashed line 33) the mixing tank 19

the AD satellite reservoir 14 to (dashed line 35) the ASB tank 18

FIG. 7 illustrates various conduits used to recycle heat from thecontents. Conduits are represented as circles and dashed lines. Forexample, conduit 2-4 to 2-2 recycles heat from the AD treated biomass 51from the AD tank 12 to the biomass effluent 6 leaving the mixing tank19. In another example, conduit 2-3 to 2-2 recycles heat from the ASBtreated biomass 8 from the ASB tank 18 to the biomass effluent 6 leavingthe mixing tank 19. In another example, conduit 2-3 to 2-1 recycles heatfrom the ASB treated biomass 8 from the ASB tank 18 to the biomass 58that enters the mixing tank 19.

An example includes that heat be recycled to heat at least one of thetanks. Also, a heat exchanger may be used to heat the contents beingrecycled from at least one environment to at least one otherenvironment. For example, a heat exchanger may heat the contents fromthe AD tank 12 to the ASB tank 18. Solar energy may also be used to heatcontents from one environment to the other environment. For example,solar energy may be used to heat the contents from the AD tank 12 to theASB tank 18.

Heat recovery may be significant. Recycling heat back to the ASB tank 18or mixing tank 19 may help maintain respective temperatures. With an ASBtank 18 that is thermophilic, for example, at a temperature of about 75°C. and an AD tank 12 that is non-thermophilic, for example, at atemperature of about 40° C., the heat directed to the ASB tank 18 may besignificant. In addition to recycling heat to an environment, heatrecovery systems may be implemented to power another environment.

In addition to recycling and heating, example reactors may includepurification treatments. For example, biomass 58 or biomass effluent 6may first go through a purification processing treatment before beingtreated within the ASB tank 18. Separation and purification of thetreated biomass 58 from the ASB tank 18 can occur, for example, by oneor more of semi-permeable membranes, centrifuge purification,distillation, filtration, industrial chromatography with zeolites,sorption, and other known mechanical and chemical means.

Also, various contents from environments may be purified for a separateprocess. Turning to FIG. 8, examples are provided that show contentstaken from an environment and purified for a separate process. Contents20 a and 20 b from the mixing tank 19 are purified for respectiveprocesses 1 a and 1 b. Contents 21 a and 21 b from the ASB tank 18 arepurified for respective processes 2 a and 2 b. Contents 22 a and 22 bfrom the AD tank 12 are purified for respective processes 3 a and 3 b.Contents 10 a, 10 b, and 10 c are purified for respective processes 4 a,4 b, and 4 c. In an example, at least a portion of the ASB treatedbiomass from the ASB tank 18 is purified and concentrated for at leastone other process outside of the AD tank 18. The portion of the ASBtreated biomass 21 a, 21 b may be separated, or separated and purified,to be used for a process outside of the AD tank 12. For example, atleast a portion of the unsolubilized components may be reintroduced intothe ASB tank 18 for future ASB digestion.

In an example, at least a portion of the ASB treated biomass serves as afeedstock or reagent for crude oil or fuel production or as at least oneprecursor for at least one synthetic process or other process. Inanother example, biogas methane is the portion of AD biogas that isseparated and used as one or more precursors for at least one syntheticprocess or other process. Examples of synthetic processes includeoxygenated aromatic compounds for synthesis of medicines and newmaterials.

Purification may occur before separation as well. In an example, atleast a portion of the AD biogas from the AD tank 12 is purified in arespective processing treatment (not shown) before being separated intodifferent contents 22 a and 22 b or before being used to produce a purebiogas.

In another example, contents recycled as shown in FIG. 7 are purified.For example, contents from the AD tank 12 may go through a purificationprocessing treatment (not shown) before being received within the ASBtank 18.

In an example, the AD tank 12 may provide at least one nutrient to theASB tank 18 before the ASB tank 18 treats the biomass. In anotherexample, the AD satellite tank 14 provides at least one nutrient to theASB tank 18 before the ASB tank 18 treats the biomass 6. In anotherexample, the AD tank 12 mixes and heats biomass with water and providesCO₂ and nutrients from the AD tank 12 to the ASB tank 18 before the ASBtank 18 treats the biomass. The contents being provided may or may nothave been recycled by the environment providing them.

In one example, bicarbonate or another base from the AD tank 12 isrecycled to the ASB tank 18 to maintain growth conditions. In anotherexample, at least a portion of CO₂ and nutrients are removed from the ADtank 12 and recycled to at least one of the mixing tank 19 and the ASBtank 18 to displace oxygen or air.

FIG. 18 includes a graph that shows the alkalinity achieved by recyclingbicarbonate from the AD tank 12. Tests show that alkalinity from ADeffluent can be used to raise the alkalinity of the ASB tank 18.

In another example, oxygen is removed from at least one of the AD tank12 and ASB tank 18 and any input streams with or without recycling. Inan example, CO₂ and bicarbonate produced in the AD environment arerecycled to the ASB environment to mitigate pH changes and reduce oxygenconcentration in the ASB environment. Oxygen removal can be accomplishedby flushing the AD 12 and ASB tanks 18 with CO₂ from combustion or gasprocessing or by other removal means. Note that contents being recycledor released may be in a gas phase, liquid phase, dissolved in asolution, or in another form.

During ASB treatment in the ASB tank 18, the pH level naturally dropsand becomes acidic. Bicarbonate ions that are formed in the AD tank 12may be removed from the AD tank 12 and put back into the ASB tank 18,which neutralizes the pH level of the ASB tank 12. In this manner,matter in the AD tank 18 is recycled in the ASB tank 12. This act maymake it unnecessary to buy a base to neutralize the pH level in the ASBtank 12, and is thus a cost-saving step. In another example, an ammoniascrubber (not shown) is included in the system to scrub contents thatare recycled from the AD tank 12. The scrubber strips out ammonia andkeeps the concentration below a toxic level.

Example Reactor Systems

The description and examples below are provided, followed by referenceto FIGS. 9-14 in relation to principles discussed herein.

An example reactor for conversion of biomass into biogas comprises anASB treatment tank containing anaerobic organisms and an AD tank thatreceives ASB tank effluent. The ASB tank receives biomass effluent thatincludes non-solubilized lignocellulosic components and treats thebiomass effluent under conditions such that the anaerobic organismsreproduce and solubilize the lignocellosic components. Upon receivingthe ASB tank effluent, the AD tank contains anaerobic bacteria thatconvert organism metabolic products of the lignocellulosic componentsinto biogas under anaerobic digestion conditions. Outputs from the ADtank including the biogas and a slurry of undigested biomass.

An example reactor may further comprise a mixing tank where the biomassis mixed with water, heated, and components in the biomass aresolubilized. The effluent of biomass suspended in water from the mixingtank is then transferred to the ASB tank.

An example reactor may further comprise at least one satellite reservoirthat provides at least one of a bacteria, nutrient, and other contentdiscussed herein, to at least one of the ASB tank and AD tank accordingto principles discussed herein.

An example reactor further comprises an AD tank that contains anaerobicbacteria and that receives contents comprising solubilized biomass. Theanaerobic bacteria is to convert organism metabolic products oflignocellulosic components of the solubilized biomass into biogas underanaerobic digestion conditions. Outputs from the AD tank include thebiogas and a slurry of undigested biomass. An AD satellite reservoir isused to supply one or more microbial species to the AD tank to supportconversion of the organism metabolic products.

An example method of converting biomass into biogas includes 1) treatingbiomass in an ASB environment with anaerobic organisms that solubilizeand metabolize lignocellulosic components of the biomass and then 2)treating the treated biomass in an AD environment with archaea andanaerobic bacteria that convert products of the lignocellulosiccomponents in the treated biomass into biogas under anaerobic digestiveconditions.

Another example method of converting biomass into biogas includes thatbiomass received by the ASB environment is 1) at least partiallysolubilized by at least one of chemical or mechanical treatment prior tothe biomass being introduced into the ASB environment. Further examplesinclude that the biomass is solubilized by at least one of chemical ormechanical treatment in the mixing tank prior to the biomass beingintroduced into the ASB tank.

An example method may further comprise providing conditions to producebicarbonate in the AD environment. The bicarbonate may be recycled tothe ASB environment.

An example method further comprises mixing and heating the biomass withwater before treating the biomass in the ASB environment.

An example method further comprises recovering heat from one of more ofthe AD environment and the ASB environment.

An example method further comprises buffering the ASB environment toproduce acetate and lactate as part of the solubilized components. TheASB environment may further be operated to produce predominantlyacetate, with little or no carbon dioxide.

An example method further comprises favoring ASB acetate ion productionover lactate ion production within the ASB environment to produce areduced CO₂ stream in the AD environment.

Large scale production of converting biomass into biogas is anticipatedbased on examples and principles discussed herein.

Alternatives include no power generation, such that the motors arereplaced by, or used in conjunction with, electrical generators.

In an example, CO₂ and bicarbonate that are produced in the AD tank arerecycled back to the ASB tank.

At least a portion of the biogas may be biogas methane that is burned byan AD electrical generator. In this manner, the AD tank provides its ownpower to the system.

Turning to FIG. 9, a reactor is shown that includes an ASB tank 602 andan AD tank 612.

Turning to FIG. 10, a reactor is shown that includes a mixing tank 702,an ASB tank 708, and an AD tank 712.

Turning to FIG. 11, a reactor is shown that includes a mixing tank 802that mixes and heats, an ASB tank 808, and an AD tank 812.

Turning to FIG. 12, a reactor is shown that includes a mixing tank 902,an ASB tank 908 that includes an ASB satellite reservoir 936, and an ADtank 912.

Turning to FIG. 13, a reactor is shown that includes a mixing tank 1002,an ASB tank 1008 that includes an ASB satellite reservoir 1036, and anAD tank 1012 with an AD satellite reservoir 1040.

Turning to FIG. 14, a reactor is shown that includes a mixing tank 1102,two ASB tanks 1108 a and 1108 b, an ASB satellite reservoir 1104 thatprovides one or more of bacteria, trace nutrients, or other matter tothe two ASB tanks 1108 a and 1108 b, and two AD tanks 1112 a and 1112 b,each AD tank having its own respective AD satellite reservoir 1140 a and1140 b.

Other reactors are anticipated that incorporate principles discussedherein.

Section A

Example Kinetic Model

A possible model describes ASB treatment with acetate as the major ASBtreatment product.

The ASB tank in this model includes the following example reactions:Cellulose(s)+H₂O(l)→glucose(aq) andglucose(aq)+3OH⁻(aq)→3CH₃COO⁻(aq)+3H₂O(l)d[CH₃COO⁻]/dt=−ΔGc=−(ΔG°+RT ln([CH₃COO⁻]³/[OH—]³[glucose])[CB]d[glucose]/dt=k ₄[active enzyme][substrate sites]−(⅓)d[CH₃COO⁻]/dtd[CB]/dt=k ₅[CB]→d[CB]/[CB]=k ₅ t→ln([CB]/[CB]₀)=k ₅(t−t₀)→[CB]_(t)=[CB]₀ e ^(k5(t−t0))d[substrate sites]/dt=a[(TSS)₀−(d(TSS)_(t) /dt)]d[active enzyme]/dt=d[CB]/dt=(n _(CB0) e ^(k7t))/V_(ASB)An example kinetic model for an ASB treated substrate may be used forthe ASB effluent that enters the AD tank.

The AD tank in this model includes the following example reactions:CH₃COO⁻(aq)→CH₄(g)+HCO₃ ⁻(aq)and VS→CH₄(g)+CO₂(g)d[CH₃COO⁻]V_(l) /dt=−d(P_(CH4)V_(g)/RT)/dt=Δ ₈Gc=(Δ₈G°+RTln(P_(CH4)[HCO₃ ⁻]/[CH₃COO⁻]))[acetoclastic methanogens]d[CH₃COO⁻]/dt=−k ₈[CH₃COO⁻][acetoclastic methanogens]d[VS]=−k ₉[VS][oxidative methanogens]=d(2bP_(CO2)V_(g)/V_(l)RT)/dt

Symbols

s, I, aq=solid, liquid, gas phase

[ ]=concentration of substance

Δ_(n)G=Gibbs energy change for reaction n

Δ_(n)G°=standard Gibbs energy change for reaction n

c=conductance

R=gas constant

T=absolute (Kelvin) temperature

CB=C. bescii

k_(n)=rate constant for reaction n

t=time

n_(CB0)=number of C. bescii cells at time=0

V_(ASB)=volume of ASB tank

V_(l)=liquid volume in AD tank

V_(g)=volume of biogas produced to time t

P_(x)=pressure of x

VS=volatile solids input to AD

TSS=total suspended solids input to ASB

a=cellulose sites per TSS

b=accessible sites per VS

Some possible results are anticipated as follows—

1. The C. bescii inoculum does not survive or grow as it should. In thatcase, the treated and control AD tank results should be very close tothe same.

2. If glucose is produced from cellulose much faster than C. bescii candigest it, then ASB effluent in the AD tank produces gas at a higherrate than the control but the methane content is not as high as itshould be.

3. If the ASB tank is fed at too high a concentration of substrate, theC. bescii grows to a stationary phase and stops making enzymes beforeASB treatment is complete. In this case, the biogas from the treatedmaterial is greater and produced faster and has a higher methanecontent, but does not get good carbon conversion to biogas.

The ASB treatment tanks in the model may be filled according to

V_(t)=V₀e^(kt)

V_(t)=volume at time t

V₀=volume at time zero with C. bescii seed

t=time in hours

k=constant depending on doubling time of C. bescii on a particularsubstrate

Table B shows exemplary k value corresponding to doubling time.

TABLE B doubling time/hours k/hours⁻¹ 2 0.346574 2.5 0.277259 3 0.2310493.5 0.198042 4 0.173287 4.5 0.154033 5 0.138629

Implementing the model above should maintain an exponentially growingculture and maximize output of exozymes.

To further design the treatment, the following formulas may be helpful—

Gas composition from stoichiometry of carbon going into AD tank.C_(in)=2×CH₃COO⁻+3yCH₃CH(OH)COO⁻+6zC₆H₁₂O₆(products of ASB treatment)C_(out) =aCH₄ +bCO₂ +cHCO₃ ⁻(products of methanogenesis)x, y, z, a, b, and c are in units of moles of compound.From the reactions of methanogenesisxCH₃COO⁻ +xH₂O=xCH₄ +xHCO₃ ⁻ yCH₃CH(OH)COO⁻ +yH₂O=yHCO₃⁻+1.5yCH₄+0.5yCO₂zC₆H₁₂O₆=3zCH₄+3zCO₂a=x+1.5y+3zb=0.5y+zc=x+y

If x, y and z (acetate, lactate, and glucose) are measured and total Cin the filtered solution come from ASB treatment, gas composition andbicarbonate production can be predicted.

Discussion of Chemistry and Thermodynamics

This is a discussion of chemistry and thermodynamics of anaerobic andthermophilic pre-digestion with C. bescii followed by anaerobicdigestion to produce biogas from organic wastes as a renewable energysource.

ASB Digestion with C. bescii.

An example of the present process according to principles discussedherein takes place in three consecutive tanks:

1. An organic waste containing polymeric materials suspended in water isfirst added to a mixing tank at 75° C. where some hydrolysis occurs. O₂is removed by a reaction with organic material, and the suspension ispasteurized.

2. Digestion with C. bescii takes place in an ASB tank at 75° C. Thepre-digestion reactions in the ASB tank includes:

Hydrolysis of polymeric material catalyzed by exozymes produced by C.bescii

Lignin+H₂O→oligomers of substituted phenolics

Cellulose+H₂O→glucose, C(H₂O)

Polyhydroxyalkanoates+H₂O→hydroxyalkanoates

These hydrolysis reactions are all exergonic, i.e. the Gibbs energychange is negative and relatively rapid at 75° C. The rate of reactionis proportionate to the concentration of enzyme and number of sites forattack on the polymeric substrate.d[products]/dt=k _(cat)[exozymes][polymer surface area]

For the reaction to proceed, conditions must be such that ΔG isnegative. ΔH⁰≈0 and ΔS° is also small, so ΔG° is also small,particularly at low temperature. Therefore, to obtain a significantlynegative ΔG requires removal of products to keep [products] small and anelevated temperature to obtain a significant rate. Use of ahyperthermophile is required to obtain commercially viable rates. (Fungithat do this at low temperature are all extremely slow growing.)Products are removed by metabolism by C. bescii and by dilution byincoming material from the mixing-hydrolysis tank.

Some of the products of hydrolysis are then metabolized by C. bescii asfollows—C(H₂O)→acetic acid, CH₃COOH and lactic acid,CH₃CH(OH)COOHCH₃COOH+HCO³⁻→CH₃COO—+H₂O+CO₂(g)CH₃CH(OH)COOH+HCO³⁻→CH₃CH(OH)COO—+H₂O+CO₂(g)

Other saccharides are metabolized similarly to glucose.Hydroxyalkanoates are also metabolized by C. bescii, but the productsare unknown. All of these reactions are intracellular. The firstreaction is a disproportionation reaction and has near zero Gibbs energychange. The second and third reactions are acid-base reactions thatproduce gas and have a significant negative Gibbs energy change thatpowers the growth and activities of C. bescii. ΔG°=−9 kJ/mole, ΔH° is −9kJ/mole, and ΔS° is ≈0 for the reaction to produce CO₂(aq). The entropyof CO2(g) is 158 J/K mole, so ΔG°≈−56 kJ/mole at 25° C. for thereactions as written. ΔG° at 80° C. is ≈−65 kJ/mole.

ΔG° values (kJ/mole) for reaction of various bases with acetic andlactic acid are given in Table D.

TABLE D ΔG° values (kJ/mole) for reaction of various bases with aceticand lactic acid are given in the Table. base acid HCO₃ ⁻(aq) OH⁻(aq)NH₃(aq) CaCO₃(s) acetic −17.5 −52.8 −25.8 +17.1 lactic −22 −58 −31 +12

Because these reactions in the sequence are the only reactions withrelatively large negative ΔG values, production of CO₂ gas, water, andother products from reaction of the acids produced with a base isessential for growth of C. bescii. Note that −ΔG gets numericallysmaller as the concentration of acid anion increases, so the reactionmay slow as these concentrations increase and there may be a practicallimit for bases other than bicarbonate. ΔG is sufficiently large andnegative for bicarbonate ion that this limit will not be reached inrealistic systems buffered with this base.

These processes are related to the growth rate of C. bescii which isalso relatively fast with doubling times of 2 to 5 days depending on thesubstrate (See Table A1 above).

3. The products of the reactions in the ASB tank are transferred to theanaerobic digestion (AD) tank where the reactions may be as follows—CH₃COO⁻+H₂O→CH₄(g)+HCO₃ ⁻(100% CH₄)2CH₃CH(OH)COO⁻+2H₂O→3CH₄(g)+2HCO₃ ⁻+CO₂(g)(75% CH₄)2C(H₂O)→CH₄(g)+CO₂(g)(50% CH₄)

The methane may thus be increased. The methane content of the biogasproduced from anaerobic digestion of each of these substrates is givenin parentheses. When catalyzed by acetoclastic methanogens, thesereactions are relatively fast with half times of 2 to 5 days dependingon the concentrations of substrates. The oligomers of substitutedphenolics are probably not metabolized by acetoclastic methanogens, butare partially metabolized by oxidative methanogenesis to produce biogaswith about 60% methane. The chart in FIG. 14 shows the methane contentof the biogas produced by differing mixtures of acetate, lactate, andglucose.

The bicarbonate produced in these reactions maintains the pH in the ADtank at slightly basic levels, so no further pH control is necessary.Note that bicarbonate ion is not volatile and will not contribute asignificant amount of CO₂ to the biogas as long as the AD pH is aboveneutral. The amount of bicarbonate produced by AD is the same as theamount of bicarbonate consumed by the reactions in the ASB tank.Therefore, bicarbonate from the AD can be recycled to supply most or allof the bicarbonate needed in the ASB reactions.

Process Variables

Mixing/Hydrolysis Tank Process Variables

1. O₂ concentration in the feedstock.

2. Feedstock composition, e.g. waste activated sludge (WAS) or manure

ASB Tank Process Variables

1. % solids in suspension fed to ASB

2. temperature

3. pH

4. Bacteria (e.g., C. bescii) concentration and phase, i.e. exponentialgrowth or stationary

5. Recycle or base addition rate

6. Stirring rate

7. Retention time in ASB

8. Alkalinity

9. Redox potential

Note that there are at least two processes in the ASB Tank, namely,hydrolysis of the feedstock and metabolism of the products ofhydrolysis. The rates of these two processes have differing dependencieson variables 1 through 5. The composition of the effluent that is fed tothe AD tank thus has a multivariate dependence on all of the abovevariables. The composition of the effluent from ASB tank determines thecomposition of the biogas produced by anaerobic digestion and theoptimum conditions for anaerobic digestion operation.

AD Tank Process Variables

1. Composition of ASB effluent

2. Retention time

3. Temperature

4. pH

5. Bacteria and Archaea concentration and phase (e.g., relative andabsolute concentrations)

6. Stirring

7. Alkalinity

8. Redox potential

Other Variables that Affect the Process

1. Sulfur chemistry

2. Nitrogen chemistry

3. Micronutrients

4. Augmentation of AD with acetoclastic methanogens

5. Growth rates of ASB bacteria (e.g., C. bescii) on differentsubstrates

Governing equations for engineering the system. //fix below

Governing Equations for ASB

Measurement as f(Time)

Rate of growth of ASB bacteria (e.g., C. bescii, etc.)d[n]/dt=kn[n]

# of live C. bescii/LRate of metabolismd[Pm]/dt=−km[n][Sm]COD of supernatant, OAc—, Lac-Rate of hydrolysisd[Ph]/dt=−kh[E][Sh]VSS, enzyme activity, COD

Variable Definitions

[n]=concentration of ASB bacteria (e.g., C. bescii), number/liter

[Sm]=concentration of substrates for metabolism, Cmol/liter

[Pm]=concentration of products of metabolism, Cmol/liter

[Sh]=concentration of substrates for hydrolysis, Cmol/liter

[E]=concentration of active enzyme, enzyme activity units/liter

[Ph]=concentration of products of hydrolysis, Cmol/liter

(dVf/dt)=flow rate of feedstock, liters/hour

VASB=volume of ASB tank, liters

[Sin]=concentration of volatile solids in feedstock, Cmol/liter

The ks are all rate constants with units determined by variables in theequation.

CONCLUSIONS

Solution to these differential equations will depend on feedstock, butin general there are two maxima, one that maximizes [Pm] and one thatmaximizes [Ph]. Short ASB retention times (around 12-20 hours) maximizes[Pm] and longer ASB retention times (around 48+ hours) maximizes [Ph].The output from AD depends on which you maximize. Maximizing [Pm]maximizes the methane content in biogas and maximizing [Ph] maximizestotal biogas and waste destruction.

These equations are based on an assumption that all of the volatilesolids can be hydrolyzed and solubilized. That can easily be fixed ifnecessary by adding a constant multiplier on Sh.

Governing equations for AD.

The output from the ASB is the input to AD, which has two components:

Products of C. bescii metabolism, i.e. acetate and lactate, atconcentration [Pm].

Products of hydrolysis from enzymatic action, i.e. saccharides,polyphenols, hydroxyalkanoates, etc. with a total concentration of [Ph].[Ph]=[acetate]+[lactate]+[saccharides]+[hydroxyalcanoates]+[polyphenols]in Cmol/literdCH₄/dt=−0.5d[acetate]/dt−0.5d[lactate]/dt−0.5d[saccharides]/dt−xd[hydroxyalcanoates]/dt−yd[polyphenols]/dtx=CH₄/Cmol hydroxyalkanoate, y=CH₄/Cmol polyphenold[CO₂]/dt=−0.16d[lactate]/dt−0.5d[saccharides]/dt−ad[hydroxyalcanoates]/dt−bd[polyphenols]/dta=CO₂/Cmol hydroxyalkanoate, y=CO2/Cmol polyphenold[HCO₃⁻]/dt=−0.5d[acetate]/dt−0.33d[lactate]/dt−cd[hydroxyalcanoates]/dtc=HCO₃ ⁻/Cmol hydroxyalkanoate

Conclusions

These equations are based on an assumption that all volatile solids aredigested.

Recycle to recover bicarbonate has not been included, but could be byadding more terms to the equations.

Engineering tank volumes

Relative tank sizes determine retention time in a continuous flow system

-   -   VH=(dV/dt)*10 hours    -   VASB=(dV/dt)*(doubling time)    -   VAD=(dV/dt)*(t %) (t %) is the time required to obtain a set        percentage of potential biogas production.    -   VH/VASB/VAD=1/0.82/7.2 to 1/0.82/14 for manure    -   VH/VASB/VAD=1/0.7/8.3 to 1/0.7/11.2 for WAS

The invention has been described with reference to various specific andpreferred embodiments and techniques. Nevertheless, it is understoodthat many variations and modifications may be made while remainingwithin the spirit and scope of the invention.

What is claimed is:
 1. An anaerobic digestion system that treats biomasscomprising lignocellulose for biogas production comprising: a syntheticmicrobial community of two metabolically cooperating digestionenvironments with different reaction conditions, (1) an anaerobicsecretome bioreactor (ASB) reactor environment where hydrolysis,acidogenesis, and acetogenesis occurs and (2) an anaerobic digestion(AD) reactor environment where methanogenesis occurs, feed receivingstructure receiving feed containing biomass that compriseslignocellulose and directing into the ASB reactor environment the feedcontaining biomass that comprises lignocellulose, the ASB reactorenvironment a synthetic microbial community consisting of at least oneselected from extremophile thermophilic anaerobic microorganisms thatare essentially acidogens and acetogens that produce secretome withexozymes for digestion the biomass through hydrolysis, acidogenesis, andacetogenesis to solubilize and metabolize a major portion of thelignocellulose, the ASB reactor environment being of a thermophilictemperature 70 to 85 degrees Celsius to support growth of the ASBextremophile thermophilic anaerobic microorganisms under essentiallyacidogenic, acetogenic, and non-methogenic conditions, and to pasteurizethe thermophilic synthetic microbial community from non-thermophilicmicroorganisms, biomass directing structure-directing ASB treatedbiomass from the ASB environment to the AD reactor environment, thepasteurized ASB treated biomass essentially free of non-thermophilicmicroorganisms, the ASB treated biomass comprising liquid effluentcontaining solubilized biomass products and metabolized biomassproducts, and solid effluent; the AD reactor environment a syntheticmicrobial community of selected non-thermophilic (NT) anaerobicmicroorganisms that digest the ASB treated biomass throughmethanogenesis to produce methane, the AD reactor environment being of atemperature to support growth of the non-thermophilic syntheticmicrobial community of non-thermophilic (NT) anaerobic microorganismsconduit to recycle contents or heat between the ASB and the AD reactorenvironment.
 2. The anaerobic digestion system of claim 1, thethermophilic anaerobic microorganisms being bacteria that comprise atleast one bacterium of genus Caldicellulosiruptor, Clostridium,Hermoanaerobacterium, and other bacteria with comparable or otherwisesuitable properties for digesting at least one lignocellulosic material.3. The anaerobic digestion system of claim 1, further comprising a heatexchanger or cooler to cool ASB effluent produced by digesting thetreated biomass in the AD reactor environment, and a conduit to recyclethe AD or ASB effluent to the ASB reactor environment.
 4. The anaerobicdigestion system of claim 1, additionally comprising separatingstructure separating at least a portion of the ASB treated biomass to beused for another process outside the AD reactor environment, includingreintroduction of the unsolubilized component back into the ASB reactorenvironment for future predigestion.
 5. The anaerobic digestion systemof claim 1, the AD reactor environment further comprising at least onesupply of bacteria and nutrients that is maintained to support theproduction of biogas with the treated biomass.
 6. The anaerobicdigestion system of claim 5, wherein the at least one supply of bacteriaand nutrients are provided by an AD satellite reservoir.
 7. Theanaerobic digestion system of claim 5, wherein the at least one supplyof bacteria and nutrients in a AD satellite reservoir are grown on asubstrate that is the same or similar to the biomass in the AD reactorenvironment.
 8. The anaerobic digestion system of claim 1, furthercomprising an ASB satellite reservoir that maintains and provides atleast one of bacteria, nutrient, and other matter to the ABS reactorenvironment as desired or needed to at least do one of the following— 1)to maintain bacteria culture suited for the ABS reactor environment, 2)to alleviate the need for trace elements to be added to the ABS reactorenvironment, depending on feedstock chemical characteristics, 3) tocondition bacteria culture to utilize the feedstock present in the ABSreactor environment 4) to speed up the ASB treatment process in the ABSreactor environment by avoiding time that otherwise would be requiredfor the bacteria culture to grow in the ABS reactor environment, and 5)to add a base to the ABS reactor environment to maintain pH and supportmetabolism; and 6) to promote digestion of the biomass.
 9. The anaerobicdigestion system of claim 1, further comprising a mixing tank that mixesbiomass with water under conditions that mitigate pH changes and promotehydrolysis of the biomass prior to the biomass being directed to the ABSreactor environment.
 10. The anaerobic digestion system of claim 9,further comprising a biogas conditioner, the biogas conditioner toremove CO₂ from the biogas and recycle it to at least one of the mixingtank, the ABS reactor environment, and the AD reactor environment todisplace oxygen or air from the biogas.
 11. The anaerobic digestionsystem of claim 1, wherein the conduit is communicably attached betweenthe AD reactor environment and the ASB reactor environment, the conduitto recycle heat from combustion gases produced in the AD reactorenvironment to the ASB reactor environment.
 12. The anaerobic digestionsystem of claim 1, wherein the conduit is communicably attached betweenthe AD reactor environment and the ASB reactor environment, the conduitto recycle from the AD reactor environment to the ASB reactorenvironment content that includes at least one of bicarbonate and carbondioxide, the bicarbonate used to control the pH of the ASB reactorenvironment and the carbon dioxide to displace oxygen or air within theASB reactor environment.
 13. The anaerobic digestion system of claim 1,further comprising a mixing tank that mixes the biomass with water withthe effluent directed to the ASB reactor environment, and wherein thecontent from the AD reactor environment is recycled to at least one ofthe mixing tank and ASB environment by means of the conduit in claim 1or a different conduit.
 14. The anaerobic digestion system of claim 1,further comprising at least one of an ASB satellite reservoir and an ADsatellite reservoir to supply contents to the respective ASB reactorenvironment and AD reactor environment, the contents including at leastone of bacteria, nutrient, or other matter that are maintained inconditions similar to the respective ASB reactor environment and ADreactor environment to which they are supplied.
 15. An anaerobicdigestion system that treats biomass for biogas production comprising: asynthetic microbial community of two metabolically cooperating digestionenvironments with different reaction environments, (1) an anaerobicsecretome bioreactor (ASB) reactor environment and (2) an anaerobicdigestion (AD) reactor environment, receiving structure receiving a feedcontaining biomass that comprises lignocellulose and that has beenmixed, heated, and had oxygen removed, and directing into the ASBreactor environment the feed containing biomass, the ASB reactorenvironment a synthetic microbial community consisting of at least oneselected from thermophilic anaerobic microorganisms that consistessentially of non-methanogenic acidogens and acetogens to digest thebiomass through hydrolysis, acidogenesis, and acetogenesis to solubilizea major portion of the lignocellulose, the ASB reactor environment beingof a thermophilic temperature and pH to support growth of thethermophilic anaerobic organisms under essentially acidogenic,acetogenic, and non-methogenic conditions, and to pasteurize the biomassof non-thermophilic microbes, directing structure directing ASB treatedbiomass from the ASB environment to the AD reactor environment, thepasteurized ASB treated biomass essentially free of non-thermophilicmicroorganisms, the AD reactor environment being of a temperature and pHto support growth of non-thermophilic (NT) anaerobic microbes thatinclude anaerobic bacteria and archaea, that digest the ASB treatedbiomass through methanogenesis to produce methane.
 16. The anaerobicdigestion system of claim 15, further comprising at least one of an ASBsatellite reservoir communicably attached to the ABS reactorenvironment, the ASB satellite reservoir to supply contents to the ASBenvironment, and an AD satellite reservoir communicably attached to theAD reactor environment, the AD satellite reservoir to supply contents tothe AD reactor environment.
 17. The anaerobic digestion system of claim15, wherein the ASB reactor environment provides a controlled oxygenlimit, a controlled temperature range, a controlled pH that maintainsoptimal growth of the thermophilic anaerobic organisms, and a controlledalkalinity.
 18. The anaerobic digestion system of claim 15, additionallycomprising structure that is communicably attached between the ADreactor environment and the ASB reactor environment, the structure torecycle bicarbonate produced in the AD reactor environment to the ASBreactor environment and thereby control the alkalinity.
 19. Theanaerobic digestion system of claim 15 wherein the thermophilicanaerobic microorganisms of the ABS reactor environment includebacteria, and the non-thermophilic, anaerobic microorganisms of the ADreactor environment include one or both of mesophilic bacterial andarchaea.
 20. An anaerobic digestion system that treats biomasscomprising lignocellulose for biogas production comprising: twoenvironments with different reaction conditions, (1) an anaerobicsecretome bioreactor (ASB) reactor environment where hydrolysis,acidogenesis, and acetogenesis occurs and (2) an anaerobic digestion(AD) reactor environment where methanogenesis occurs, feed receivingstructure receiving feed containing biomass that compriseslignocellulose and directing into the ASB reactor environment the feedcontaining biomass that comprises lignocellulose, the ASB reactorenvironment containing at least one selected from extremophilethermophilic anaerobic microorganisms that are essentially acidogens andacetogens that digest the biomass through hydrolysis, acidogenesis, andacetogenesis to solubilize and metabolize a major portion of thelignocellulose, the ASB reactor environment being of a thermophilictemperature 70 to 85 degrees Celsius to support growth of the ASBextremophile thermophilic anaerobic microorganisms under essentiallyacidogenic, acetogenic, and non-methogenic conditions, and to pasteurizethe biomass from non-thermophilic microorganisms, biomass directingstructure-directing ASB treated biomass from the ASB reactor environmentto the AD reactor environment, the pasteurized ASB treated biomassessentially free of non-thermophilic microorganisms, the ASB treatedbiomass comprising liquid effluent containing solubilized biomassproducts and metabolized biomass products, and solid effluent; the ADreactor environment comprising non-thermophilic (NT) anaerobicmicroorganisms that digest the ASB treated biomass throughmethanogenesis to produce methane, the AD reactor environment being of atemperature to support growth of the the non-thermophilic syntheticmicrobial community of non-thermophilic (NT) anaerobic microorganismsconduit to recycle contents or heat between the ASB and the AD reactorenvironment.